1. Field of the Invention
The subject invention generally pertains to electric motors for wet carpet cleaners and more specifically to a seal and bearing assembly for such a motor.
2. Description of Related Art
The motors of some vacuum cleaners, such as wet/dry shop vacs and wet carpet cleaners, are exposed to a significant amount of moisture-laden air. Some motors include one or more bearing seals to protect the bearings and other motor components from the moisture. The motors disclosed in U.S. Pat. No. 6,472,786, for example, include one seal that engages the motor shaft and a support cushion that sits between the bearing and the fan end bracket.
The method used for retaining seals and bearings can affect the axial position of the motor shaft relative to the motor's stator, which can thus affect the relative axial position of the motor's commutator and its brushes. In the '786 patent, for instance, the bearing protection system permits some change in the shaft's axial position due to the compressibility of the support cushion and the way the inboard bearing is mounted.
Even a slight shift in the axial position of the shaft can greatly diminish the life and performance of the motor. A motor's brushes normally wear a track in the commutator, as the shaft rotates at about 20,000 to 30,000 rpm. An axial shift in the position of the shaft could force the brushes slightly out from within their tracks. As a result, portions of the brushes may lift slightly away from the surface of the commutator, which can cause electrical arching between the brushes and the commutator.
Since flexible or compressible seal materials typically creep under load, it can be difficult to provide a motor with a bearing seal whose compressibility does not at least partially determine the axial position of the motor shaft. Thus, a need exists for an improved seal and bearing assembly that ensures that a motor shaft is maintained at a substantially fixed axial position regardless of the seal's compression.